Since photographic sensitive materials are generally composed of an electrically insulating base and photographic layers, static charges are frequently accumulated when the materials are subjected to friction or separation caused by contacting with the surface of the same or different materials during steps for production of the photographic sensitive materials or in the case of using them for photographic purposes. These accumulated static charges cause many problems. The most serious problem is discharge of accumulated static charges prior to development processing, by which the sensitive emulsion layer is exposed to light to form dot spots or branched or feathery linear specks when development of the photographic films is carried out. This phenomenon is the so-called static mark, by which a commercial value of the photographic films significantly deteriorates, and is sometimes entirely lost. For example, in the case of medical or industrial X-ray films, it is easily understood that the static marks may result in a very dangerous judgement or misdiagnosis. This phenomenon is a very troublesome problem, because it becomes clear for the first time by carrying out development. Further, these accumulated static charges are also the origin of secondary problems such as adhesion of dusts to the surface of films, uneven coating, etc.
As described above, such static charges are frequently accumulated in the cases of producing and using photographic sensitive materials. For example, in the step for production, they are generated by friction of the photographic film contacting a roller or by separation of the emulsion face from the base face during a step for rolling or unrolling. Further, they are generated on X-ray films in an automatic camera by contacting with or separating from mechanical parts or fluorescent sensitizing paper, or they are generated by contact with or separation from rollers and bars made of rubber, metal, or plastics in a bonding machine or an automatic developing machine in the developing shop or in a camera in the case of using color negative films or color reversal films. In addition, they are generated by contact with packing materials, etc.
Static marks on photographic sensitive materials occurring due to accumulation and discharge of static charges increase with increases in the sensitivity of the photographic sensitive materials and an increase of the processing speed. Particularly, static marks are easily generated because of high sensitization of the photographic sensitive materials and severe processing conditions such as high speed coating, high speed photographing, and high speed automatic treatment.
In order to prevent these troubles caused by static charges, it is suitable to add antistatic agents to the photographic sensitive materials. However, antistatic agents used conventionally in other fields cannot be used freely for photographic sensitive materials, because they are subjected to various specific restrictions due to the nature of the photographic sensitive materials. Namely, it is required for the antistatic agents capable of use in the photographic sensitive materials that not only is the antistatic ability excellent, but also that they do not have adverse influences upon photographic properties of the photographic sensitive materials, such as sensitivity, fog, granularity, sharpness, etc., that they do not have an adverse influence upon film strength of the photographic sensitive materials (namely, that the photographic sensitive materials are not easily injured by friction or scratching), that they do not have an adverse influence upon adhesion resistance (namely, that the photographic sensitive materials do not easily adhere when the surfaces of them are brought into contact with each other or with surfaces of other materials), that they do not accelerate deterioration of processing solutions for the photographic sensitive materials, and that they do not deteriorate adhesive strength between layers composing the photographic sensitive materials, etc. Accordingly, applications of antistatic agents to photographic sensitive materials are subject to many restrictions.
One method for overcoming problems caused by static charges comprises increasing electric conductivity of the surface of the photographic sensitive material so that static charges disappear within a short time, prior to spark discharging of the accumulated charges.
Accordingly, processes for improving the electrically conductive property of the base or the surface of various coating layers in the photographic sensitive materials have been proposed hitherto, and utilization of various hygroscopic substances, water-soluble inorganic salts, certain kinds of surfactants and polymers, etc., has been attempted. For example, it has been known to use polymers as described in U.S. Pat. Nos. 2,882,157, 2,972,535, 3,062,785, 3,262,807, 3,514,291, 3,615,531, 3,753,716, 3,938,999, etc., surface active agents as described in U.S. Pat. Nos. 2,982,651, 3,428,456, 3,457,076, 3,454,625, 3,552,972, 3,655,387, etc., and metal oxides and colloidal silica as described in U.S. Pat. Nos. 3,062,700, 3,245,833, 3,525,621, etc.
However, many of these substances exhibit great specificity, depending upon the kind of film base or the photographic composition, and there are cases that, although they produce a good result on certain specific film bases, photographic emulsions or other photographic elements, they are not only useless for preventing generation of static charges in case of using different film bases and photographic elements, but also have an adverse influence upon photographic properties.
On the other hand, there are many cases wherein, although they have excellent antistatic effects, they can not be used because of having an adverse influence upon photographic properties such as sensitivity, fog, granularity, sharpness, ect. For example, it has been well known that polyethylene oxide compounds have antistatic effects, but they often have an adverse influence upon photographic properties, such as increasing fog, desensitization, deterioration of granularity, etc. Particularly, in sensitive materials in which both sides of the base are coated with photographic emulsions, such as medical direct X-ray sensitive materials, it has been difficult to develop techniques for effectively providing an antistatic property without having an adverse influence upon photographic properties. Thus, the application of antistatic agents to the photographic sensitive materials is very difficult, and their use is often limited to a certain range.
Another method for overcoming the problems of photographic sensitive materials caused by static charges is that which comprises controlling the triboelectric series of the surface of the sensitive materials to reduce generation of static charges caused by friction or touching as described above.
For example, it has been attempted to utilize fluorine containing surface active agents, as described in British Pat. Nos. 1,330,356 and 1,524,631, U.S. Pat. Nos. 3,666,478 and 3,589,906, Japanese Patent Publication No. 26687/77 and Japanese Patent Application (OPI) Nos. 46733/74 and 32322/76 (the term "OPI" as used herein refers to a "published unexamined Japanese patent application"), etc., for photographic sensitive materials for the above-described purpose.
However, photographic sensitive materials containing these fluorine containing surface active agents generally have an electrostatic property of charging in negative polarity. Accordingly, although it is possible to adapt the triboelectric series of the surface of the sensitive materials for each triboelectric series of rubber rollers, Delrin (linear polyoxymethylene type acetal resin) rollers and nylon rollers by suitably combining the fluorine containing surface active agents (having an electrostatic property of charging in negative polarity) with a non-fluorine type surface active agents having an electrostatic property of charging in positive polarity, problems still occur, because the triboelectric series of the surface of the sensitive materials cannot be simultaneously adapted for all triboelectric series of rubber rollers, Delrin rollers and nylon rollers. That is, when such prior fluorine containing surface active agents are used so as to adapt for rubber, branched static marks occur due to Delrin, of which triboelectric series is situated on the positive side comparing to the triboelectric series of rubber; and when they are used so as to adapt for Delrin, spot static marks occur due to the rubber, of which triboelectric series is situated on the negative side comparing to the triboelectric series of Delrin.
For the purpose of compensating for this fault, there are processes which comprise reducing the surface resistance by using high molecular electrolytes together therewith. However, they also produce adverse effect; for example, they cause deterioration of adhesion resistance and have an adverse influence upon photographic properties. Accordingly, it is impossible to incorporate them so as to provide a sufficient antistatic property.
Furthermore, it is well known that the photographic sensitive materials are prepared by applying a subbing layer, silver halide photographic emulsion layers, a protective layer, a filter layer, an antihalation layer and an intermediate layer, etc., to a base composed of cellulose acetate, polyester, or polyethylene laminated paper, etc. In the case of producing photographic sensitive materials having such many layers, it is required to apply coating solutions so as to form a uniform thin layer without causing problems such as "relelling" (i.e., a very small spot which is uncoated with a coating solution), etc. Furthermore, in the case of producing photographic sensitive materials, sometimes the photographic emulsions and other gelatin containing coating solutions are applied to the base at the same time to form a multilayer structure. For example, in order to produce a color photographic sensitive material, three or four photographic emulsion layers are formed simultaneously by continuous application. In the case of applying gelatin or another colloid solution to such a gelatin colloid layer, it is very difficult to obtain coating properties required for such a case as compared with the case of applying the gelatin colloid solution directly to the base. It is particularly difficult in the case wherein the layer to be applied is a wet layer set by cooling just after application. Hitherto, although many fluorine containing surface active agents have been used as antistatic agents, most of them have inferior coating ability, particularly in high speed applications, and they cause formation of "comets" or "repelling", i.e., local imperfect coating caused by dusts and unevenness.
U.S. Pat. No. 4,013,696 has disclosed an art wherein nonionic surface active agents are used together. However, this art is useful only for specified photographic coating solutions or under specified coating conditions, and lacks wide applicability.